# Spindles - Lingering Questions **URL:** \ **Category:** Uncategorized\ **Created:** [November 1, 2021, 1:59pm UTC](https://forum.onefinitycnc.com/t/spindles-lingering-questions/8643 "2021-11-01T13:59:54Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![349iq2345](https://avatars.discourse-cdn.com/v4/letter/3/bb73d2/32.png) [@349iq2345](https://forum.onefinitycnc.com/u/349iq2345)\ **Post date:** [November 1, 2021, 2:20pm UTC](https://forum.onefinitycnc.com/t/spindles-lingering-questions/8643/2 "2021-11-01T14:20:02Z")
Hey Jim, > [@Webb](#): > > I’ve read here about space limitations and the OF Z unit. Will a 65mm unit fit the OF properly, with no modifications to either device? It depends on - the exact spindle length (datasheet) and - the position of the spindle in the holder (mine has a mark) and - the distance between protruding Z stepper and spindle’s top end taking into account the actual Z slider’s one of three possible mounting positions. With respect to all this I would measure it then. Since I’m waiting for my machine yet, I can’t do it. Maybe someone else can? > [@Webb](#): > > If the 65mm choice creates problems, my next move will be to the 80mm 1.5KW ER16 collet unit. Once the Onefinity 80 mm spindle holder was released I ordered it and I came accross the question whether to buy a 2.2 kW spindle with ER16 or with ER20 collet. The first takes tool shanks from 1-10 mm and the latter from 1-13 mm, which would mean half-inch tools. But since at first I did not expect to use tools larger than 8 mm, I was unsure. So I asked the [manufacturer](https://www.mechatron-gmbh.de) and he answered, the spindle with ER20 collet has larger bearings and a stiffier shaft. Larger bearings means longer life. Stiffier shaft means more precision. Also one should take into consideration that when using tools with a larger shank, the thicker the shank the stiffier the tool and so the longer the tools you can use – and thus the deeper the pockets you can mill into your workpiece. So I went for the [ER20 spindle](https://www.spindel-shop.de/en/High-Frequency-Spindle-standard-Series/High-Frequency-Spindle-HFS-series/Water-Cooled-HF-Spindles--HF-Spindle--HF-Spindles--HF-Spindle--HF-Spindles--Motorspindle--Milling-Spindle--Grinding-Spindle-4.html). > [@Webb](#): > > Is wiring a quality VFD really that much of a challenge? Surely not. I’m currently studying different VFD’s User manuals in order to create a wiki entry. VFDs are complex but using the basic functions (and most beginners rarely need more) is definetely not Rocket Science. --- _[View the full topic](https://forum.onefinitycnc.com/t/spindles-lingering-questions/8643)._